14 CIRCULAR 6 5 9, U. S. DEPARTMENT OF AGRICULTURE 



moisture requirement of the air cannot be satisfied so long as the tem- 

 perature of the cooling surfaces remains markedly lower than that of 

 the air. 



Storage With Other Products 



Apples absorb odors very readily, and it is therefore undesirable 

 to store them with other products that have pronounced odors. This is 

 particularly true of potatoes and other root crops, which often impart 

 an "earthy" flavor to apples. Since apples give off ethylene, a gas that 

 stimulates respiration and ripening, the potential keeping quality of 

 other products stored with apples may be adversely affected. This is 

 particularly true of cut flowers, which may be caused to shed their 

 petals or are otherwise injured by ethylene (18) . 



Fungus Diseases 



There are many fungus diseases of apples that can cause serious 

 losses under certain conditions. Fortunately, however, most of these 

 are primarily orchard diseases and are controlled on the harvested 

 fruit by the sprays that good growers apply to control them in the 

 orchard. However, if they are present on the stored fruit, they 

 respond to storage temperatures about the same as do the physiological 

 processes of the fruit already discussed (p. 8). All of them develop 

 rapidly and are most destructive at warm temperatures, whereas at 

 30° to 32° F. many will not develop at all, or at the most very slowly, 

 particularly if the apples are not ripe. The spores of most rot organ- 

 isms will not germinate at 30° to 32°, but if infection has already 

 occurred when apples reach this temperature, most of the rots will 

 persist during storage and the causal organism will resume growth 

 after the fruit is removed to a warm temperature. Detailed informa- 

 tion regarding the diseases of apples in storage can be found in United 

 States Department of Agriculture Miscellaneous Publication 168 (13) 

 and Farmers' Bulletin 1160 (3). Discussion can be limited here to a 

 relatively few diseases that are especially influenced by harvesting, 

 handling, and storage operations; most of these are not due to fungi 

 but are functional or physiological in nature. 



The storage disease responsible for most of the decay in apples 

 after harvest is blue mold rot. caused by the fungus Perdcillium ex- 

 pansum Link. It is primarily a wound parasite and ordinarily re- 

 quires some kind of mechanical injury to infect an apple. This rot 

 is very soft and watery and has a pronounced musty odor. It gets its 

 name from the bluish masses of spores that appear on the surface of 

 affected areas (fig. 5, A ) . This fungus is omnipresent wherever apples 

 are grown, and its spores are found in large numbers on the surfaces 

 of apples as they are picked and brought in for packing. Since the 

 fungus is ordinarily incapable of penetrating the sound, uninjured 

 skin of the apple, careful handling of the fruit at all times is a prime 

 requisite in preventing infection. Bruising and other mechanical 

 injuries lead to blue mold infection. 



Although blue mold enters apples most often through mechanical 

 injuries, it sometimes enters through open lenticels in the skin, 

 through the stem, especially when this is enlarged or fleshy and has 



